Pathology III Bone Tissue Flashcards
Cretinism or “Christ-like”
Is one of the disorders of the growth plate
A 3 y/o pt. presents with mental retardation, dwarfism, and a failure of fontanelle closure. The pt. was born with umbilical hernias, coarse facial features, and hypotonic posture. Mother had iodine deficiency while pregnant.
Cretinism
Why are the children mentally retarded in cretinism?
defective issues in the formation of the neural tube
Why do we used iodinated salt in the US?
To prophylax
maternal iodine deficiency leads to cretinism
What do you look for in fontanelle closure?
Look at the front of the children’s heads
Which cells are affected in cretinism?
Chondrocytes do not follow an orderly progression and there is a failure of ossification
How is cretinism different from achondroplasia?
The dwarfs are not mentally retarded in achondroplasia
How is cretinism tx?
Many Sx are resolved by administering thyroid hormone
A 9 y/o presents with mental retardation, corneal opacities, hearing defects, cardiac valve disturbances, and DENTAL DEFECTS. What is the mechanism of this disorder?
A deposition of glucosaminoglycans in developing bones
MORQUIO SYNDROME
What type of mucopolysacchariodosis is morquio syndrome?
Type IV
Compare morquio syndrome to cretinism and achondroplasia
A severe form of dwarfism but overall more like cretinism than achondroplasia
A dwarf patient has the head of a typical size with a small body
Achondroplastic patient
What causes achondroplasia
the arrest of the growth plate
What type of dwarfism is presented in achondroplasia
An inheritied dwarfism
What is the most common disease of the growth plate?
Achondroplasia
A pt whose heterozygous parents are affected shown sign of dwarfism with shorted limbs
Achondroplsia
Autosomal dominant condition
Decrease of paracrine signaling (FGF)
The parents will have 25% change of having normal children
Type I collagen disease
Osteogenesis imperfecta or “brittle bone disease”
A defect in the extracellular protein, collegen I
In addition to skeleton, what other sites are affected in osteogenesis imperfecta?
The sites highly rich in type I collagen : joints eyes ears skin teeth
Where is the deficiency in type I collagen?
Osteoblasts
Type I collagen are mainly present in what?
Bone and sclera (fibrocartilage)
Diagnosis of osteogenesis imperfecta
Presence of BLUE SCLERA
A Pt. presents with multiple fractures in the lower limbs over the course of a few years. Physical exam reveals blue sclera. The pt. opts for amputation.
Osteogenesis imperfecta
What condition, other than osteogenesis imperfecta, can cause blue sclera?
Tetracycline overdose- will also cause blue ears
Diseases associated with defects in metabolic pathway
Osteopetrosis
Why is the juvenile version of osteopetrosis lethal?
Because the calvarium gets very thick in this case and causes herniation of the brain through foramen magnum, atlas, axis, and vertebral canals
Osteopetrosis
marble bone disease (marbles are rocks) and “albers-shonberg disease”
What does diffuse skeletal sclerosis mean in osteopetrosis
Sclera = means hard
Petro=rock like e.g. petrous part of the temporal bone
The bones are abnormally brittle and fracture like a piece of CHALK
What happens to the bones in the body of someone who has osteopetrosis?
The rate of synthesis > the rate of degradation
So over time, the bones of the body become very large
What is unique about the architecture of the bone in osteopetrosis?
Not the way it should be like a trabecular bone (with proper arrangement and collagen deposition)
-Cannot resist tensile forces the way most bone can
Osteopetrosis: Autosomal Recessive vs dominant
Malignant - recessive
Benign - dominant
serious genetic defects tend to be recessive since people don’t make it to reproductive age
4 types of osteopetrosis
Infantile malignant form (letal)
Type II carbonic anhydrase deficiency - probably an inability to produce carbonic acid in order to breakdown the bone
Autosomal dominant type I and II
3 stages of Paget Disease
osteoclast dysfunction
- osteolytic stage
- mixed osteoclastic-osteoblastic stage
- predominant osteoblastic acitivity
What age group for paget?
Adults!
Differentiate osteoporosis from pager’s
age of onset!!!!
PAGET starts mid-adulthood
What geographical location is paget RARE?
asia and africa
Which cytokine is a potent osteoclastic stimulator?
IL-6
Paramyxovirus causes IL-6 to be released and cause what disease?
PAGET
Chalk-like fx are present in which two diseases?
osteopetrosis and PAGET
How does Paget become noticeable in clinical setting?
incidental
by x-ray - big bones
paget is benign
won’t present with a lot of sx
Lab tests that indicate PAGET’s ?
increase serum hydroxyproline
increase serum alkaline phosphatase
indicate bone breakdown (initial problem)
Anterior bowing
shown in pager’s disease because femur is affected
this is different from lateral bowing in rickett’s and osteomalacia
A 30 year old patient complains of pain in the leg and presents with anterior bowing
paget’s
pain caused by bone overgrowth and compression of nerves
also vessels are compressed and cause ischemia
What are the two serious complications of Paget’s ?
osteoarthritis
increased risk of malignant osteosarcoma
increased association with arteriovenous malformation
Osteosarcoma resulting from Paget’s
FIND THE NODULES OF OSTEOSARCOMA AT THE SPINE (doesn’t break the rule of primary osteosarcoma since in this case it is secondary to another disease like paget’s)
look elsewhere in the body to find nodules at above and below the knee
also look for serum levels of hydroxyproline and alkaline phosphatase
AV shunting in Paget’s
high cardiac output
heart failure
redness over AV shunt on chest
Vit D deficiency
Rickett’s
Osteomalacia
bone isn’t formed properly because ineffective mineralization of the osteoid secreted by osteoblasts
Differentiate Rickett’s from Osteomalacia
Rickett’s in KIDS
Osteomalacia in ADULTS
Hyperparathyroidism
PTH plays a central role in calcium homeostasis by stimulating osteoclasts to increase bone resorption = MOBILIZE CALCIUM
The patient has high serum calcium and PTH levels
suspect hyperPTH
Hypercalcemia
cause dementia
Vit D synthesis is stimulated by which hormone?
PTH
a osteoporotic patient is given calcium. the person developed parathyroid tumor, what happens?
more PTH released
more calcium in the system
DEMENTIA
Iatrogenic dementia
from calcium supplement to patients with osteoporosis who develops PTH tumor
Osteomyelitis
inflammation of bone and marrow
A patient infected with s. aureus who inflammation of the bone and marrow
pyogenic osteomyelitis
blood-borne
through vasculature
A sickle cell patient infected with what agent will have inflammation of the bone and marrow
salmonella
pyogenic osteomyelitis
A patient infected with TB will develop mycobacterial osteomyelitis
POTT’s disease
What is pot’s disease
mycobacterial osteomyelitis
